As exemplified in FIG. 19(a), an implement for construction equipment such as hydraulic excavators includes a boom 51, an arm 52 and a bucket 53 as chief components. Many coupling devices for these components are used in parts such as rotating sections where the components are linked; hydraulic cylinder sections where they are operated; and coupling sections where they are coupled to the vehicle body. FIG. 19(b) (exploded perspective view) shows the structure of a bucket coupling section in details. Implement bushings 54, 55 provided for the coupling section have, in their respective inner circumferential surfaces, a grease lubricating groove and a thermally hardened layer which has a hardness of HRC 45 or more and is formed by carburization quenching or induction hardening in order to attain improved seizure resistance and wear resistance. Also, implement pins 56, 57, 58 have, in their respective outer circumferential surfaces, a thermally hardened layer which has a hardness of HRC 45 or more and is formed by induction hardening or carburization quenching in order to achieve improved seizure resistance, wear resistance and breakage resistance. Further, in the coupling sections where the implement bushings 54, 55 are coupled to the implement pins 56, 57, 58, there is formed a nipple for injecting lubricating grease. This nipple allows the grease to be supplied from outside to the contact surfaces through a grease hole defined in the implement bushing and through the grease groove in the inner circumference of the implement. Sealing devices 59, 60 are also provided to prevent an escape of the lubricating grease present between the implement bushing and the implement pin and penetration of earth, sand and muddy water, whereby occurrence of seizure between the inner circumferential surface of the implement bushing and the outer circumferential surface of the implement pin is prevented and, in consequence, improved wear life is ensured.
The grease supply mechanism similar to one described above is applied to implement coupling devices for other construction equipment than the hydraulic shovel shown in FIG. 19(a). Such implement coupling devices are provided at high positions. In many cases, with the intention of overcoming inconveniences for operation, a lubricating grease feeding pipe is used for feeding grease from a convenient position.
If the lubricating grease runs out, seizure, abnormal noise (squeak), abnormal wear and the like will occur at the coupling sections, and therefore, grease feeding needs to be done at intervals of 24 to 50 hours in the actual circumstances. The grease feeding has, however, failed in completely preventing occurrence of seizure, abnormal noise (squeak), abnormal wear etc. at the coupling sections.
If seizure, abnormal noise (squeak), abnormal wear or the like occurs at the coupling section where an implement bushing and an implement pin are coupled, there arises a need for replacement of not only the implement bushing and but also the implement pin, which disadvantageously involves troublesome replacement work and increased cost.
For easy maintenance of implements, various metal based sintered contact materials having good seizure resistance and good oil retention performance have been recently applied to implement bushings. The effect of use of such materials in terms of characteristics is not much more than prolongment of the greasing intervals to about 250 to 500 hours of time. It is still the case that the grease feeding pipes and similar parts have not been disused yet and no satisfactory measure has been developed for cost reduction.
In view of the improvements in the operating efficiency of construction equipment and the environment of the job sites, there exist an imperative need for reduction of the total weight of an implement and improved absorbability for noise occurring at the coupling sections. In addition, weight saving of the coupling sections themselves is a task to be tackled.
The invention has been directed to overcoming the foregoing problems and a primary object of the invention is therefore to provide a coupling device for equipment implements, which coupling device does not impair the lubricity of bearing sections when the equipment is in service, does not cause seizure during rotation of bearings, does not need frequent feeding of grease to the bearing section from outside, and provides good noise absorbability.